1. Field of the Invention
This invention concerns the improvements made to reactors for heterogeneous synthesis. It concerns more particularly a system to increase the yields of reactors for heterogeneous synthesis and more particularly for the synthesis of ammonia, comprising a catalytic layer partly connected to a boiler, a catalytic layer substantially run through by a heat exchanger, and at least one intermediate catalytic layer.
2. Description of the Related Art
Reactors of the type described above are known per se and are the object of Italian patent No. 28961-66.
In order to establish matters straight away and to make it as easy as possible to understand the invention, FIG. 1 (partial cross-section with a plan showing the reactor's axis) outlines a reactor design according to the patent in question.
The synthesis gas GS enters from 10, flows from top to bottom through airspace 21 between the internal wall 22 of the shell M and the external wall 23 of the cartridge CU, flows upwards from the bottom F0 (following arrow F1) running through the inside of tubes Ti of the heat exchanger SC, flows axially (arrow F2) through the intermediate catalytic layer CC, is cooled in the first branch of the boiler CA from the top of which it leaves in order to penetrate (arrow F3) the top catalytic layer CS, through which it runs axially from top to bottom leaving according to arrow F4 and flowing again upwards as F'4 which enters tube BP which takes it as flow F5 directly into the lower catalYtic layer CI from which it flows as F'5 to continue upwards inside exchanger SC from the top of which it is sent downwards as F7 flowing through central tube 25' and leaving this as reacted gas F'7.
Arrow F8 indicates the conduction of water to the boiler and arrow F9 indicates the exit from the boiler of the vapour produced therein by recovering reaction heat. Since the reactor in question is known it is not described in detail herein, such description being available in the abovementioned Italian patent No. 28961-66 which is deemed to be incorporated herein.
Reactors of the type described above, although already remarkably improved when compared to the technology available up to the moment when they made their appearance, suffered from a number of disadvantages which in the long run became an obstacle to the success which it seemed reasonable to expect from them.
Among the disadvantages in question, mention should be made in particular of those connected with the axial flow of the synthesis gas through the catalytic beds, of the ensuing pressure drops and of the need to use a large size catalyst in order to limit the pressure drop in question.